From the start, the NFL has played games on Thanksgiving Day based on the tradition of college football games being played around the Thanksgiving holiday. The NFL’s Thanksgiving Day games have traditionally included one game hosted by the Detroit Lions—since 1934—and one game hosted by the Dallas Cowboys—since 1966. Starting in 2006, a third prime time game was added on Thanksgiving. Unlike the afternoon games, this game has no fixed host and commonly features division rivals.
The Tradition
Most agree Princeton and Rutgers played the first-ever football game on Nov. 6, 1869. A few weeks later, members of the Young American Cricket Club and the Germantown Cricket Club played a football match on Thanksgiving Day in Philadelphia. The sport itself had just been born and looked more like a combination of rugby and soccer in those days with formal rules established later.
The NFL
A few professional football leagues developed throughout the country in the early part of the 20th century. In 1920, several teams came together to form the American Professional Football Association which later became the National Football League. Following the league’s formation, the NFL struggled to distinguish itself from other football leagues and was slow to develop a consistent fan base. Several NFL teams were quick to adopt the Thanksgiving Day game as a way to draw in new fans. NFL games quickly became a national staple of Thanksgiving Day, and the league and its broadcast partners reaped the benefits as the games grew in popularity to the level that we see today.
Sources:
https://en.wikipedia.org/wiki/NFL_on_Thanksgiving_Day
https://www.wivb.com/news/timeline-how-football-became-a-thanksgiving-tradition/
